The invention relates to armored cable and flexible cord.
Armored cable typically has a metal sheath (the armor) enclosing one or more individually insulated conductors, e.g., wires. The metal sheath may be formed of a helically interlocked continuous strip of metal, or a smooth or corrugated continuous metal tube.
Armored cable is used in constructing commercial wiring systems to distribute electricity for lighting or convenience power. Typically, a number of segments of armored cable are used in a wiring system, for example, that provides power to a series of lighting fixtures in a ceiling. The segments of armored cable in the wiring system must be connected to each other and also to conductors from the lighting fixtures. These connections conventionally are made on-site by linking the ends of the cable, and also the conductors from the fixtures, using cable connectors, wire nuts, and miscellaneous hardware.
Modular armored cable assemblies are known. Such assemblies include a precut segment of armored cable having a modular connector attached to each end. A modular connector generally includes a housing assembly with a port for receiving the end of a segment of armored cable and a metal or plastic housing. A modular connector also typically includes one or more plastic connector inserts containing electrical contacts through which an electrical connection is made between conductors from the armored cable and conductors in a modular connector on another segment of armored cable. Generally, the modular connector at one end of a cable assembly may include a connector insert with female channels or male leads that match the female channels and may also include a modular connector at the other end of the cable assembly of similar construction.
Modular cable assemblies can be pre-assembled in the desired lengths, with the appropriate modular connectors, and then transported to the installation site of the wiring system. The armored cable assemblies then can be attached sequentially and connected electrically to the electrical panels and their loads in order to provide the wiring system.
The invention relates generally to electrical connectors, e.g. modular connectors for use with armored cable and flexible cord. The modular connectors can also be used, e.g., in a modular cable assembly.
In particular, the modular connectors are configured for contact sequencing such that electrical contacts in one portion of a connector connect with electrical contacts in a matching portion of the connector in a predetermined, specified sequence. That is, by staggering the positions of the contacts within the connector portions, the contacts connect together at different times (i.e., not simultaneously) when the connector portions are mated together.
In some applications, e.g., alternating current applications that use three-phase power with inductive loads, connectors connect all three phases of the system using one connector pair. In cases where there is an inductive electrical load at high voltages, each one of these three phases can produce a high-power electrical arc. Therefore, disconnecting all three phases at the same time can produce three high-power arcs simultaneously.
By sequencing the mating and unmating time for the contacts in the connectors, e.g., by disconnecting two of the three phases before the third phase, the amount of arcing in the first two phases can be minimized or eliminated and the amount of power dissipation from the remaining electrical arc can be minimized. Thus, the risk of electrical arcing is minimized, which reduces the risk of danger to personnel, the risk of fire, and/or the possible degradation to the connector. Moreover, because the amount of electrical arcing that the connector material preferably needs to withstand is reduced, cost-effective materials can be used to produce the connectors. The contact sequencing described herein can also be applied to other connectors used in electrical systems having multiple, e.g., greater than three, phases, or in connectors used in three-phase systems and carrying multiples of the three phases, particularly where electrical arcing can result.
Other features and advantages of the invention will be apparent from the description of the preferred embodiments thereof, and from the claims.